Planning your DataStax Distribution of Apache Cassandra upgrade

Minimizing downtime.

The upgrade process for DataStax Distribution of Apache Cassandra™ (DDAC) provides minimal downtime (ideally zero). During this process, upgrade and restart one node at a time while other nodes continue to operate online. With a few exceptions, the cluster continues to work as though it were on the earlier version of DDAC until all of the nodes in the cluster are upgraded.

Factors to consider when planning an upgrade:

Reduce risks
You can reduce risks and effort by employing a continual upgrade strategy to provide access to product improvements and new features and reduce version impacts. Ensure that you repair your nodes regularly. Node repair ensures that data on a replica is consistent with data on other nodes.
Version impacts
Upgrades are impacted by the version you are upgrading from and the version you are upgrading to. The greater the gap between the current version and the target version, the more complex the upgrade.
Backup data

DataStax recommends backing up your data prior to any version upgrade, including logs and custom configurations. A backup provides the ability to revert and restore all the data used in the previous version if necessary.

Upgrade order
Upgrade order matters. Upgrade nodes in this order:
  1. In multiple datacenter clusters, upgrade every node in one datacenter before moving on to other datacenters.
  2. Upgrade the seed nodes within a datacenter first.